Testing Wifi Association Behavior

Wifi delays have a big effect on user experience

Delays from Wifi are one of the biggest reasons why end users end up having
a bad experience when trying to use the network. In addition to the latency caused
by retransmissions, the speed at which devices associate and re-associate is a factor
that is mostly unseen by the end user but can result in serious frustration. Testing
Wifi association behavior is one of the most basic metrics to gain about your DUT
at this layer.

Wifi tests in CDRouter

While there are plenty of ways to examine Wifi behavior and its affect on user
experience by testing
things like applicaiton latency, CDRouter contains a wifi.tcl test module
that specifically exercises Wifi association in a number of ways.

Wifi client restart

disassociation and association may behave differently in each device depending
on the order in which the address assigned with DHCP is released, if at all. The
first three tests in the CDRouter wifi.tcl exercise this in three different ways:

disassociation and association when the address is released and renewed
(also called “graceful restart”)

disassociation and association when the address is not released, but DHCP
is restarted on the station

disassociation and association when the address is not released, nor renewed

Given the stateful nature of these systems, a DUT may arrive in a bad state depending
on the order in which these are done.

Wifi mode compatibility

In its initial beacons, Wifi endpoints advertise which phy and security modes they
support. When the DUT advertises a large set of these, it’s important to test that
it will allow a station to connect using those options. Our test in CDRouter
attempts to connect using all advertised modes and combinations of modes to make sure
the DUT will actually accept connections using these modes. This also involves making
sure the beacon advertisements are conformant.

Wifi association stress testing

The meat of Wifi association testing comes from performance - can a Wifi router or
AP sustain repeated disassociation and association at high frequency? As we like to
stress in our other performance related tests, repeated, normal protocol behavior
may be slowly generating memory leaks or other issues that will cause a DUT to eventually
fail in sometimes catastrophic ways.

Testing the base functionality of your Wifi implementations overall, in addition to
physical layer testing, is key to ensuring you’ll have robust products for your customer
or end user.